Sprayable coating compostion

ABSTRACT

The present invention relates to a sprayable coating composition comprising a) at least one isocyanate reactive compound comprising at least one thiol group, b) at least one polyisocyanate functional compound, and c) a catalyst comprising at least one organic metal compound where the metal is a metal of Groups 3 to 13 of the Periodic Table. The invention also relates to use of the sprayable coating composition as a clear coat, its use as a clear coat, its use as a clear coat in a multi-layer lacquer coating, and its use in the refinish industry and in finishing large transportation vehicles.

[0001] The invention relates to a sprayable coating composition, its useas a clear coat, its use as a clear coat in a multi-layer lacquercoating, and its use in the refinish industry and in finishing largetransportation vehicles.

[0002] Coatings used for painting motor vehicles and repairing theoriginal paint are required to have good physical properties such ashardness, mechanical strength, and resistance to water, acids, andsolvents. The coatings are also required to have good appearanceproperties, which means that films must be smooth and have a high glossand a high distinctness of image. It is also desirable that allproperties are retained under prolonged outdoor weathering.

[0003] For environmental reasons, it is required to use a coatingcomposition which can be applied easily using spray application at a lowvolatile organic content (VOC). Coatings with a lower organic solventcontent emit lower levels of solvent when they are used, and so theatmosphere becomes less polluted.

[0004] U.S. Pat. No. 4,788,083 discloses a sprayable coating compositioncomprising a hydroxyl compound, an isocyanate, a metal catalyst selectedfrom tin and bismuth, and a molar excess of a complexing agent such as amercapto compound. Although tin and bismuth catalysts are known metalcatalysts for the hydroxyl isocyanate reaction, it has been found thatthese metal catalysts do not catalyse the thiol isocyanate reaction.Furthermore, the mercapto compound in U.S. Pat. No. 4,788,083 is used tocomplex and thus deactivate the metal catalyst. The activation of themetal catalyst is effectuated by heat or the addition of a tertiaryamine activator. So, the reaction of hydroxyl isocyanate only startswhen the metal catalyst is activated.

[0005] The present invention relates to a sprayable coating compositioncomprising

[0006] a) at least one isocyanate reactive compound comprising at leastone thiol group,

[0007] b) at least one polyisocyanate-functional compound, and

[0008] c) a catalyst comprising at least one organic metal compoundwhere the metal is a metal of Groups 3 to 13 of the Periodic Table.

[0009] It has surprisingly been found that sprayable coating compositioncan be provided where the thiol isocyanate reaction can be catalysed inthe presence of an organic metal compound, the metal being a metal ofGroups 3 to 13 of the Periodic Table, both at room temperature and athigher temperatures such as 60° C. At all temperatures, an excellent potlife—drying balance is shown. An additional advantage is the fact thatthere is no necessity to add a tertiary amine activator to the coatingcomposition. This addition would have a negative effect on the pot lifeof the coating composition. Furthermore, the sprayable coatingcomposition of the present invention provides excellent properties suchas were mentioned above to be necessary for its use in the refinishindustry and in finishing large transportation vehicles.

[0010] Although we do not want to be bound by any theory, it issuggested that the capacity of the organic metal compound to hydrolyseplays a significant role in the reaction mechanism of the thiolisocyanate reaction. Therefore, the reaction of thiol and isocyanatecompounds performs quite differently from the reaction of hydroxyl andisocyanate compounds in the presence of metal catalysts.

[0011] U.S. Pat. No. 5,849,864 discloses a sprayable coating compositioncomprising a polymercapto resin, a polyisocyanate, and a tin catalystcomplex. The tin catalyst is complexed with sulphonic acid. Uponexposure to an amine, the catalyst complex becomes activated. It hasbeen found that tin catalyst complexes do not catalyse the thiolisocyanate reaction. Furthermore, as mentioned above, it is adisadvantage to use amine in coating compositions. WO 98/15585 disclosesa sprayable coating composition comprising a hydroxyl compound, anisocyanate, and a catalyst which is the reaction product of a titanium,zirconium, hafnium or aluminium ortho ester, a beta-diketone orbeta-ketoester, and a complexing agent such as a mercapto compound. Thecatalyst as such can be used in the range of 0.005 to 0.5 per cent byweight with respect to the weight of the reaction mixture. Although amercapto compound is present in the coating composition, this is in suchsmall quantities that WO 98/15585 does not disclose the coatingcomposition of the present invention.

[0012] JP-A-04-063823 discloses an architectural sealant comprising acompound having two or more thiol groups per molecule, a polyisocyanatecompound, and a metallic soap. It is not disclosed or suggested how toprepare a sprayable coating composition thereof, nor is its use in aclear coat with the above-mentioned properties described.

[0013] U.S. Pat. No. 5,064,871 discloses a composition comprising anisocyanate reactive compound, a polyisocyanate, and a catalystcomprising a bismuth and a zirconium carboxylate. Although the use ofpolymercaptan as an isocyanate reactive compound is mentioned in thedescription, only polyol resins are exemplified. Furthermore, thecomposition is used in particular as an adhesive. It is not disclosed orsuggested how to prepare a sprayable coating composition thereof, nor isits use in a clear coat with the above-mentioned properties described.

[0014] U.S. Pat. No. 4,312,971 discloses a composition comprising anorganic compound comprising at least two active hydrogen atoms, apolyisocyanate, and a catalyst comprising an organo zirconium and anorgano mercury compound. Although the use of aliphatic thiols as anorganic compound comprising at least two active hydrogen atoms ismentioned in the description, only polyol resins are exemplified.Furthermore, the composition is used in particular as non-cellularpolyurethanes, and cellular rigid and flexible polyurethane foams. It isnot disclosed or suggested how to prepare a sprayable coatingcomposition thereof, nor is its use in a clear coat with theabove-mentioned properties described.

[0015] JP-A-10182786 discloses a sealant comprising a polymer having twoor more thiol groups per molecule, a polyisocyanate compound, and anorganic metal. Although it is mentioned in the description that organicmercury compounds and organic lead compounds can be used, only organictin compounds are exemplified. As already mentioned before, tin does notcatalyse the reaction of thiol and isocyanate. Furthermore, inJP-A-10182876 it is not disclosed or suggested how to prepare asprayable coating composition thereof, nor is its use in a clear coatwith the above-mentioned properties described.

[0016] The use of organic metal compounds, such as zirconium, hafnium,and aluminium complexes, in the hydroxyl isocyanate reaction isdisclosed in Florio J., Paint & Coatings Industry, Oct. 1997, pp.110-120, and in U.S. Pat. No. 5,846,897. However, it is not disclosed orsuggested that these complexes may be used in the thiol isocyanatereaction.

[0017] The catalyst comprises at least one organic metal compound wherethe metal is a metal of Groups 3 to 13 of the Periodic Table.Preferably, the metal is a transition metal. More preferably, the metalis a metal of Group 4 of the Periodic Table.

[0018] The organic metal compounds comprise metal salts and/or complexesof organic compounds. The organic compounds are groups having 2 to 40carbon atoms, optionally comprising atoms such as O, N, and S. The metalsalts comprise anions selected from the groups of carboxylates. Examplesthereof include propionate, butyrate, pentanoate, 2-ethyl hexanoate,naphthenate, oxalate, malonate, succinate, glutamate, and adipate. Themetal complexes comprise ligands selected from the group ofbeta-diketones, alkyl acetoacetates, alcoholates, and combinationsthereof. Examples thereof include acetyl acetone (2,4-pentanedione),2,4-heptanedione, 6-methyl-2,4-heptadione, 2,4-octanedione, propoxide,isopropoxide, and butoxide. Preferably, the organic metal compound is ametal complex.

[0019] Examples of metals include aluminium, titanium, zirconium, andhafnium. Examples of metal complexes include aluminium complexed with2,4-pentanedione (K-KAT® XC5218 ex King Industries), aluminium triacetylacetonate, zirconium tetraacetyl acetonate, zirconium tetrabutoxide(Tyzor® NBZ ex Dupont), titanium tetrabutoxide (Tyzor® TBT ex Dupont),zirconium complexed with 6-methyl-2,4-heptadione, K-KAT® XC6212 ex KingIndustries, aluminium triisopropoxide, and titanium diisopropoxidebis-2,4(pentadionate) (Tyzor® AA ex DuPont). These catalysts may be usedin an amount of 0.01 to 10 wt. % on solid curable material, preferably0.1 to 5 wt. %.

[0020] Examples of the isocyanate reactive compound comprising at leastone thiol group include a thiol-functional compound comprising at leasttwo thiol-functional groups and a compound comprising at least onethiol-functional group and one hydroxyl-functional group. Also mixturesof these compounds may be used in the compositions of the presentinvention.

[0021] Suitable thiol group-containing compounds are generally preparedby reacting hydroxyl group-containing compounds with thiolgroup-containing acids, such as 3-mercapto propionic acid, 2-mercaptopropionic acid, thio-salicylic acid, mercapto succinic acid, mercaptoacetic acid, or cysteine. Examples of suitable hydroxyl group-containingcompounds are diols, triols, and tetraols, such as 1,4-butane diol,1,6-hexane diol, 2,2-dimethyl-1,3-propane diol,2-ethyl-2-propyl-1,3-propane diol, 1,2-, 1,3-, and 1,4-cyclohexanediols, and the corresponding cyclohexane dimethanol, 1,1,1-trimethylolpropane, 1,2,3-trimethylol propane, and pentaerythritol. Examples ofcompounds prepared according to such a method include pentaerythritoltetrakis (3-mercapto propionate), pentaerythritol tetrakis (2-mercaptoacetate), trimethylol propane tris (3-mercapto propionate), trimethylolpropane tris (2-mercapto propionate), and trimethylol propane tris(2-mercapto acetate). Good results have been obtained with trimethylolpropane tris (3-mercapto propionate) and pentaerythritol tetrakis(3-mercapto propionate).

[0022] A further example of a compound prepared according to such amethod consists of a hyperbranched polyol core based on a starterpolyol, e.g., trimethylol propane, and dimethylol propionic acid. Thispolyol is subsequently esterified with 3-mercapto propionic acid andisononanoic acid. These methods are described in European patentapplication EP-A 0 448 224 and International patent application WO93/17060.

[0023] Other syntheses to prepare compounds comprising at least twothiol-functional groups involve:

[0024] the reaction of an aryl or alkyl halide with NaHS to introduce apendent thiol group into the alkyl and aryl compounds, respectively;

[0025] the reaction of a Grignard reagent with sulphur to introduce apendent thiol group into the structure;

[0026] the reaction of a polymercaptan with a polyolefin according to aMichael addition reaction, a nucleophilic reaction, an electrophilicreaction or a radical reaction;

[0027] the reaction of a polyisocyanate with a thiol-functional alcohol,and

[0028] the reduction of disulphides.

[0029] The compound comprising at least one thiol-functional group andone hydroxyl-functional group may for example have a structure accordingto the following formula: T[(C₃H₆O)_(n)CH₂CHOHCH₂SH]₃, with T being atriol such as trimethylol propane or glycerol. An example of such acompound is commercially available from Henkel under the trademarkHenkel Capcure® 3/800.

[0030] Alternatively, the isocyanate reactive compound comprising atleast one thiol group is a resin having as a backbone a polyester resin,polyurethane resin, polyacrylate resin, and polyether resin. Theseisocyanate reactive compounds may then also comprise hydroxyl groups.

[0031] The isocyanate reactive compound comprising at least one thiolgroup may be a polyester prepared from (a) at least one polycarboxylicacid or reactive derivatives thereof, (b) at least one polyol, and (c)at least one thiol-functional carboxylic acid. The polyesters preferablypossess a branched structure. Branched polyesters are conventionallyobtained through condensation of polycarboxylic acids or reactivederivatives thereof, such as the corresponding anhydrides or lower alkylesters, with polyalcohols, when at least one of the reactants has afunctionality of at least 3.

[0032] Examples of suitable polycarboxylic acids or reactive derivativesthereof are tetrahydrophthalic acid, tetrahydrophthalic anhydride,hexahydrophthalic acid, hexahydrophthalic anhydride, methylhexahydrophthalic acid, methyl hexahydrophthalic anhydride,dimethylcyclohexane dicarboxylate, 1,4-cyclohexane dicarboxylic acid,1,3-cyclohexane dicarboxylic acid, phthalic acid, phthalic anhydride,isophthalic acid, terephthalic acid, 5-tert. butyl isophthalic acid,trimellitic anhydride, maleic acid, maleic anhydride, fumaric acid,succinic acid, succinic anhydride, dodecenyl succinic anhydride,dimethyl succinate, glutaric acid, adipic acid, dimethyl adipate,azelaic acid, and mixtures thereof.

[0033] Examples of suitable polyols include trimethylol propane,trimethylol ethane, glycerol, 1,2,6-hexanetriol, ethylene glycol,1,2-propylene glycol, 1,3-propylene glycol, 2-methylpropane-1,3-diol,neopentyl glycol, 2-butyl-2-ethyl-1,3-propane diol,cyclohexane-1,4-dimethylol, the monoester of neopentyl glycol andhydroxypivalic acid, hydrogenated Bisphenol A, 1,5-pentane diol,3-methyl-pentane diol, 1,6-hexane diol, 2,2,4-trimethylpentane-1,3-diol, dimethylol propionic acid, pentaerythritol,di-trimethylol propane, dipentaerythritol, and mixtures thereof.

[0034] Examples of suitable thiol-functional organic acids include3-mercaptopropionic acid, 2-mercaptopropionic acid, thio-salicylic acid,mercaptosuccinic acid, mercaptoacetic acid, cysteine, and mixturesthereof.

[0035] Optionally, monocarboxylic acids and monoalcohols may be used inthe preparation of the polyesters. Preferably, C₄-C₁₈ monocarboxylicacids and C₆-C₁₈ monoalcohols are used. Examples of the C₄-C₁₈monocarboxylic acids include pivalic acid, hexanoic acid, heptanoicacid, octanoic acid, nonanoic acid, 2-ethylhexanoic acid, isononanoicacid, decanoic acid, lauric acid, myristic acid, palmitic acid,isostearic acid, stearic acid, hydroxystearic acid, benzoic acid,4-tert. butyl benzoic acid, and mixtures thereof. Examples of the C₆-C₁₈monoalcohols include cyclohexanol, 2-ethylhexanol, stearyl alcohol, and4-tert. butyl cyclohexanol.

[0036] Good results may also be obtained with an aqueousthiol-functional polyurethane dispersion which is obtainable by firstpreparing an isocyanate-functional polyurethane from diols,diisocyanates, and building blocks containing groups which facilitatethe stabilisation of the resin in an aqueous dispersion, followed byreaction of the isocyanate-functional polyurethane with a polyfunctionalthiol in a base-catalysed addition reaction, followed by dispersion inwater.

[0037] The isocyanate reactive compound comprising at least one thiolgroup may be a thiol-functional polyacrylate. Such a polyacrylate isderived from hydroxy-functional acrylic monomers, such as hydroxy ethyl(meth)acrylate, hydroxy propyl (meth)acrylate, hydroxy butyl(meth)acrylate, other acrylic monomers such as (meth)acrylic acid,methyl (meth)acrylate, butyl (meth)acrylate, optionally in combinationwith a vinyl derivative such as styrene, and the like, or mixturesthereof, wherein the terms (meth)acrylate and (meth)acrylic acid referto both methacrylate and acrylate, as well as methacrylic acid andacrylic acid, respectively. The thiol group is introduced by thereaction product of dimethyl-m-isopropenyl benzyl isocyanate andmercapto ethanol. Alternatively, glycidyl methacrylate is introducedinto the polymer to prepare an epoxy-functional polyacrylate. The epoxygroups are then reacted with suitable thiol-functional organic acidssuch as mentioned above. The polyacrylate is prepared by conventionalmethods, for instance, by the slow addition of appropriate monomers to asolution of an appropriate polymerisation initiator, such as an azo orperoxy initiator.

[0038] Also included in the coating compositions of the invention may bedi-, tri-, or higher thiol-functional diluents such as ethane dithiol orbis-beta-mercapto-ethyl sulphide. Preference is given to the use ofhigher-molecular weight thiol-functional compounds, which may beobtained by reaction of a polythiol-functional compound with apolyisocyanate.

[0039] Preferably, the isocyanate reactive compound comprising at leastone thiol group is derived from a polyester compound. Examples thereofinclude the above-mentioned reaction product of hydroxylgroup-containing compounds with thiol group-containing acids and theabove-mentioned polyester prepared from (a) at least one polycarboxylicacid or reactive derivatives thereof, (b) at least one polyol, and (c)at least one thiol-functional carboxylic acid. The most preferredthiol-functional compound is pentaerythritol tetrakis (3-mercaptopropionate).

[0040] The organic polyisocyanate includes polyfunctional, preferablyfree polyisocyanates, with an average NCO functionality of 2.5 to 5, andmay be (cyclo)aliphatic, araliphatic or aromatic in nature. Thepolyisocyanate may include biuret, urethane, uretdione, and isocyanuratederivatives. Examples of these organic polyisocyanates include1,6-diisocyanatohexane, isophorone diisocyanate, 2,4-toluenediisocyanate, 2,6-toluene diisocyanate, diphenyl methane-diisocyanate,4,4′-bis(isocyanato-cyclohexyl) methane, 1,4-diisocyanatobutane,1,5-diisocyanato-2,2-dimethyl pentane,2,2,4-trimethyl-1,6-diisocyanatohexane, 1,10-diisocyanatodecane,4,4-diisocyanato-cyclohexane, 2,4-hexahydrotoluene diisocyanate,2,6-hexahydrotoluene diisocyanate, norbornane diisocyanate, 1,3-xylylenediisocyanate, 1,4-xylylene diisocyanate, 1-isocyanato-3-(isocyanatomethyl)-1-methyl cyclohexane, m-α,α-α′,α′-tetramethyl xylylenediisocyanate, the above-mentioned derivatives thereof, and mixturesthereof. Normally, these products are liquid at ambient temperature andcommercially available in a wide range. Particularly preferredisocyanate curing agents are triisocyanates and adducts. Examplesthereof are 1,8-diisocyanato4-(isocyanatomethyl) octane, the adduct of 3moles of toluene diisocyanate to 1 mole of trimethylol propane, theisocyanurate trimer of 1,6-diisocyanatohexane, the isocyanurate trimerof isophorone diisocyanate, the uretdione dimer of1,6-diisocyanatohexane, the biuret trimer of 1,6-diisocyanatohexane, theadduct of 3 moles of m-α,α-α′,α′-tetramethyl xylene diisocyanate to 1mole of trimethylol propane, and mixtures thereof. Preferred are cyclictrimers (isocyanurates) and uretdiones of 1,6-hexane diisocyanate andisophorone diisocyanate. Usually these compounds contain smallquantities of their higher homologues.

[0041] Optionally, a water borne coating composition according to thepresent invention may also comprise an organic hydrophilicpolyisocyanate compound substituted with non-ionic groups, such as C₁-C₄alkoxy polyalkylene oxide groups. Preferably, 30 wt. % of non-ionicgroups will be present on the total solid polyisocyanate compound, morepreferably 20 wt. %, most preferably 15 wt. %. Preferred are theisocyanurates of 1,6-hexane diisocyanate and isophorone diisocyanatesubstituted with methoxy polyethylene glycol.

[0042] Optionally, a hydroxyl-functional compound comprising at leasttwo hydroxyl-functional groups may be present in the curable material.The hydroxyl-functional compound comprising at least twohydroxyl-functional groups may be selected from polyester polyols,polyether polyols, polyacrylate polyols, polyurethane polyols, celluloseacetobutyrate, hydroxyl-functional epoxy resins, alkyds, and dendrimericpolyols such as described in WO 93/17060. Also, hydroxyl-functionaloligomers and monomers, such as castor oil and trimethylol propane, maybe included. A preferred polyol is an acrylate polyol. More preferred isan acrylate polyol available from Akzo Nobel Resins having the tradename Setalux® 1157.

[0043] The polyisocyanate and the compound comprising isocyanatereactive groups should be mixed such that the ratio of isocyanate groupsto isocyanate reactive groups is in the range of 0.5-3:1, preferably0.75-2.5:1, and more preferably 1-2:1. It is preferred that at least 10%of the isocyanate reactive groups are thiol groups, more preferred atleast 25%, most preferred at least 50%.

[0044] If hydroxyl-functional compounds are present in the coatingcomposition, catalysts for the cross-linking of isocyanate groups withhydroxyl groups may be present. Examples thereof include Sn-basedcatalysts, such as dibutyl tin dilaurate and dibutyl tin diacetate.

[0045] The polyisocyanate may be mixed with the isocyanate reactivecompound by any suitable technique. However, simply stirring usually issufficient. Sometimes it may be useful to dilute the polyisocyanatesomewhat with an organic solvent like ethyl acetate or1-methoxy-2-propyl acetate to reduce its viscosity.

[0046] Optionally, a ketone based chelating agent may be added to thecoating composition. Examples of these chelating agent includebeta-dicarbonyls, alpha-hydroxyl ketones, fused aromatic beta-hydroxyketones, dialkyl malonates, aceto acetic esters, alkyl lactates, andalkyl pyruvates. Preferably, beta-dicarbonyls such as acetyl acetone areused. The ketone based chelating agent may be used in an amount up to 10wt. % on solids, preferably up to 5 wt. %.

[0047] The composition according to the present invention may be a waterborne composition, a solvent borne composition or a solvent-freecomposition. Since the composition may be composed of liquid oligomers,it is especially suitable for use as a high solids composition or asolvent-free composition. Alternatively, the coating composition of thepresent invention may be an aqueous powder coating dispersion whereinthe isocyanate reactive compound comprising at least one thiol group hasa Tg above 20° C. The coating composition may as well be used in powdercoating compositions and hot melt coatings compositions. Preferably, thetheoretical volatile organic content (VOC) in the composition is lessthan about 450 g/l, more preferably less than about 350 g/l, mostpreferably less than about 250 g/l.

[0048] The coating compositions may further comprise other ingredients,additives or auxiliaries, such as pigments, dyes, emulsifiers(surfactants), pigment dispersion aids, levelling agents, anti-crateringagents, antifoaming agents, wetting agents, antisagging agents, heatstabilisers, UV absorbers, antioxidants, and fillers.

[0049] The coating composition of the present invention may be appliedto any substrate. The substrate may be, for example, metal, plastic,wood, glass, ceramic, or some other coating layer. The other coatinglayer may be comprised of the coating composition of the currentinvention or it may be a different coating composition. The coatingcompositions of the current invention show particular utility as clearcoats, base coats, pigmented top coats, primers, and fillers.Preferably, the coating composition according to the present inventionmay be used as clear coat or as primer.

[0050] The coating compositions can be applied by conventional meanssuch as by spray gun, brush, or roller, spraying being preferred. Curingtemperatures preferably are between 0 and 100° C. and more preferablybetween 20 and 60° C. The compositions are particularly suitable in thepreparation of coated metal substrates, such as in the refinishindustry, in particular the body shop, to repair automobiles andtransportation vehicles, and in finishing large transportation vehiclessuch as trains, trucks, buses, and aeroplanes.

[0051] The composition of the present invention is also suitable forapplication by an external mixing apparatus, one where a liquidcomposition comprising at least one isocyanate-functional compound andat least one isocyanate reactive compound is sprayed via a spray nozzle,with a small amount of catalyst. Such an apparatus is described, forexample, in WO 98/41316. Due to the very effective use of the catalysts,the compositions according to the present invention have very shortcuring times, which makes this method specifically suitable for thesecompositions.

[0052] In the case of the coating composition being a clear coat, thebase coat may be a conventional base coat known in the coating art.Examples are solvent borne base coats, e.g., Autobase® ex Akzo NobelCoatings BV, based on cellulose acetobutyrate, acrylic resins, andmelamine resins, and water borne base coats, e.g., Autowave® ex AkzoNobel Coatings BV, based on an acrylic resin dispersion and polyesterresin. Furthermore, the base coat may comprise pigments (colourpigments, metallics and/or pearls), wax, solvents, flow additives,neutralising agent, and defoamers. Also high solids base coats can beused. These are, for instance, based on polyols, imines, andisocyanates. The clear coat composition is applied to the surface of abase coat and then cured. An intermediate curing step for the base coatmay be introduced.

[0053] The invention will be illustrated with reference to the followingexamples. Of course these examples are submitted for a betterunderstanding of the invention only; they are not to be construed aslimiting in any manner the scope thereof.

EXAMPLES

[0054] List of abbreviations: Penta(SH)4 pentaerythritol tetrakis(3-mercapto propionate) Other compounds used Tolonate ® HDT-LV ex Rhodiaisocyanurate of hexamethylene diisocyanate Byk ® 306 ex Byk Chemielevelling agent Tyzor ® NBZ ex Dupont zirconium tetrabutoxide (80 wt.%in n- butanol) Tyzor ® TBT ex Dupont titanium tetrabutoxide K-KAT ®XC5218 ex King Industries aluminium complexed with 2,4- pentanedioneK-KAT ® XC6212 ex King Industries zirconium complex K-KAT ® 348 ex KingIndustries bismuth carboxylate 2-ethyl hexanoic acid

Methods

[0055] A coating is cured when the mark from firm pushing with the thumbdoes not leave any imprint.

[0056] The gelling time was determined visually and is the time afterwhich the composition is no longer influenced by gravity.

Examples 1 to 11 and Comparative Examples A and B

[0057] A formulation was prepared comprising the following compounds:Penta(SH)₄ 50 ToIonate ® HDT LV 90 Byk 306(10 wt.% in butyl acetate) 7,0

[0058] To this formulation were added several organic metal compounds,optionally in combination with acetyl acetone (acac). A 50 μm thick filmwas drawn out onto tin plated metal. The drying time was evaluated atroom temperature (RT) and at 60° C. Wt. % Wt. % catalyst on solid acacadded on binders catalyst Gel time drying RT drying 60° C. 1 1% K-KAT ®XC5218 — >1 day 1 hr 18 min. 2 3% K-KAT ® XC6212 — >1 day  45 min. 15min. 3 0.5% Tyzor ® NBZ — 20 min.  15 min.  2 min. 4 0.5% Tyzor ® NBZ500% >1 day  25 min.  5 min. 5 0.5% Tyzor ® NBZ 900% >1 day  35 min.  7min. 6 0.5% Zr(acac)₄* — 10 min   6 min.  3 min. 7 0.5% Zr(acac)₄ 100% 1day  10 min.  4 min. 8 1.5% Tyzor ® TBT — 35 min.  20 min  4 min 9 0.5%Tyzor ® TBT 100% >1 day  75 min. 20 min 10 0.5% Al(iPrO)₃** —  6 min  11min  4 min 11 0.5% Al(acac)₃*** — >1 day 210 min 25 min A 1% K-KAT ® 348— >>1 h B 1% dibutyl tin dilaurate — >>1 h

[0059] These examples show that organic metal compounds where the metalis a metal of Groups 3 to 13 of the Periodic Table, such as zirconium,aluminium, and titanium compounds, are very active catalysts in thereaction between thiol and isocyanate. Their results, optionally incombination with acetyl acetone, show an excellent pot life/dryingbalance. Well-known catalysts for the reaction between hydroxyl andisocyanate like dibutyl tin dilaurate or bismuth carboxylate 2-ethylhexanoic acid show no activity at all.

1. Sprayable coating composition comprising a) at least one isocyanatereactive compound comprising at least one thiol group, b) at least onepolyisocyanate-functional compound, and c) a catalyst comprising atleast one organic metal compound where the metal is a metal of Groups 3to 13 of the Periodic Table.
 2. Sprayable coating composition accordingto claim 1, characterised in that the, metal is a transition metal. 3.Sprayable coating composition according to claim 2, characterised inthat the metal is a metal of Group 4 of the Periodic Table.
 4. Sprayablecoating composition according to claim 1, characterised in that themetal is selected from the group of aluminium, titanium, zirconium, andhafnium compounds.
 5. Sprayable coating composition according to any oneof the preceding claims, characterised in that the organic metalcompound is a metal complex.
 6. Sprayable coating composition accordingto claim 5, characterised in that the metal complexes comprise ligandsselected from the group of beta-diketones, alkyl acetoacetates,alcoholates, and combinations thereof.
 7. Sprayable coating compositionaccording to any one of the preceding claims, characterised in that aketone based chelating agent is added to the coating composition. 8.Sprayable coating composition according to any one of the precedingclaims, characterised in that at least 50% of the isocyanate reactivegroups are thiol groups.
 9. Sprayable coating composition according toany one of the preceding claims, characterised in that the isocyanatereactive compound comprising at least one thiol group is derived from apolyester compound.
 10. Use of a coating composition according to anyone of the preceding claims, comprising applying the composition as aclear coat.
 11. Use of a coating composition according to claim 10,comprising applying the composition as a clear coat in a multi-layerlacquer coating.
 12. Use of a coating composition according to any oneof preceding claims 1 to 9 in the refinish industry and in finishinglarge transportation vehicles.